Pen



FIG. 1 is a front view of a pen, showing my new design;

FIG. 2 is a back view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a perspective view thereof; and,

FIG. 8 is an exploded perspective view thereof. 

The ornamental design for pen, as shown and described. 